A variety of applications require articles to be strong, wear resistant, lightweight and to display high specific strength, high impact toughness and high flexural stiffness while being manufactured by a convenient and cost-effective method.
(2: Metal Coating Processes)
A number of metal deposition techniques including electrolytic, electroless plating and powder-coating processes are known to apply metallic coatings to surfaces of various articles such as sporting goods, automotive articles and the like.
(2.1. Electroless Coating)
Electroless coating processes are used commercially particularly for Ni, Cu and Ag. Electroless coating deposition rates are low, typically 0.25 mil/hr (6.35 μm/hr) to 0.5 mil/hr (12.7 μm/hr) and yield an amorphous microstructure. Typical coating thickness values for electroless plating processes are much lower than 1 mil (25 μm) and primarily applied to enhance the appearance, or improve the scratch and the corrosion resistance. Leibowitz in U.S. Pat. No. 3,597,266 (1971) describes a popular electroless Ni plating process.
(2.2. Conventional Electroplating)
A variety of electroplating processes are known to deposit conventional coarse-grained metallic coatings on substrates at deposition rates that typically exceed 1 mil/hr (25 μm/hr) and are commercially available for a number of chemistries including Cu, Co, Ni, Cr, Sn, Zn. In the case of galvanic coatings it is well known that after the coating has been built up to a thickness of about 5-10 μm, it tends to become highly textured and grows in a fashion whereby anisotropic and elongated columnar grains prevail with typical grain widths of a few microns and grain lengths of tens of microns. Prior art thin coatings applied by conventional electroplating processes exhibit conventional average grain sizes (≧10 μm) and do not significantly enhance the overall mechanical properties of the coated article, thus not providing a structural shell.
Donavan in U.S. Pat. No. 6,468,672 (2002) discloses a process for forming a decorative chromium plating having good corrosion resistance and thermal cycling characteristics on a plastic substrate by first depositing an electrically conductive coating on the plastic substrate followed by electrodepositing a high leveling semi-bright nickel electroplate layer, followed by electrodepositing a bright nickel electroplate layer, and finally followed by electrodepositing a chromium layer.
(2.3: Fine-Grained Electroplating)
Recently it has been recognized that a substantial reduction of the average grain size strongly enhances selected physical, chemical and mechanical properties of metallic materials. For example, in the case of nickel, the ultimate tensile strength increases from 400 MPa (for conventional grain-sizes greater than 5 μm) to 1,000 MPa (grain size of 100 nm) and ultimately to over 2,000 MPa (grain size 10 nm). Similarly, the hardness for nickel increases from 140 VHN (for conventional grain-sizes greater than 5 μm) to 300 VHN (grain size of 100 nm) and ultimately to 650 VHN (grain size 10 nm). Electroplated fine-grained metallic materials of improved durability and performance characteristics are known in the prior art including:
Erb in U.S. Pat. No. 5,352,266 (1994), and U.S. Pat. No. 5,433,797 (1995), assigned to the applicant of this application, describes a process for producing nanocrystalline metallic materials, particularly nanocrystalline nickel with an average grain size of less than 100 nm using pulse electrodeposition and an aqueous electrolytic cell. Products of the invention include wear resistant coatings and magnetic materials.
Palumbo DE 10,288,323 (2005) (=WO2004/001100 A1 2002) also assigned to the applicant of this application, discloses a process for forming coatings or freestanding deposits of nanocrystalline metals, metal alloys or metal matrix composites. The process employs tank, drum or selective plating processes. Novel nanocrystalline metal matrix composites and micro-components are disclosed as well.
(2.4: Alternative Fine-Grained Coating Processes)
Various patents disclose low temperature powder spray processes for the preparation of metallic coatings.
Alkhimov in U.S. Pat. No. 5,302,414 (1991) describes a cold gas-dynamic spraying method for applying a coating to an article by introducing metal or metal alloy powders, polymer powders or mechanical mixtures thereof into a gas stream. The gas and particles (average particle size range: 1 to 50 microns) form a supersonic jet (velocity: 300 to 1,200 m/sec) at a temperature considerably below the fusing temperature of the powder material. The jet is directed against an article of a metal, alloy or dielectric, thereby coating the article with the particles.
Tapphorn in U.S. Pat. No. 6,915,964 (2005) describes a spraying process for forming coatings by solid-state deposition and consolidation of powder particles. The subsonic or sonic gas jet containing the particles is directed onto the surface of an object. Due to the high velocity impact and thermal plastic deformation, the powder particles adhesively bond to the substrate and cohesively bond together to form consolidated materials with metallurgical bonds. The powder particles and optionally the surface of the object are heated to a temperature that reduces yield strength and permits plastic deformation at low flow stress levels during high velocity impact. No melting of the powder particles takes place.
(3: Polymeric Substrates)
Suitable permanent substrates include polymer materials, which optionally can be filled with or reinforced with, e.g., metals and metal alloys, glass, ceramics, and carbon based materials selected from the group of graphite, graphite fibers and carbon nanotubes. For strength and cost reasons, filled polymers are very desirable plastic substrate materials. The term “filled” as used herein refers to polymer resins which contain powdered (i.e., 0.2-20 microns) mineral fillers such as talc, calcium silicate, silica, calcium carbonate, alumina, titanium oxide, ferrite, and mixed silicates which are commercially available from a variety of sources having a filler content of up to about forty percent by weight. If required, e.g., in the case of electrically non-conductive or poorly conductive substrates and the use of electroplating for the coating deposition, the surface of the polymeric substrates can be metallized to render it sufficiently conductive for plating. In this case the fine-grained coating layer is always substantially thicker than the metallized layer.
Poppe in U.S. Pat. No. 3,655,433 (1972) describes nonconductive plastic substrates particularly suitable for electroplating, whereby the adhesion of the metal to the plastic material is enhanced by incorporating between 1 and 25 percent by weight of a metal resinate in the polymer. Crystalline polyolefins, such as polyethylene, polypropylene and propylene-ethylene copolymer, are modified with calcium resinate, zinc resinate, aluminum resinate, sodium resinate, potassium resinate or ammonium resinate to improve the adhesion of metal thereto.
Ding in U.S. Pat. No. 6,509,107 (2003) discloses polyolefin compositions that are well suited to metal plating and are easily processed into articles by various molding methods. The blends of the invention preferably include polyolefin homopolymers or copolymers, acrylonitrile-butadiene-styrene polymers, and a blend of at least one styrene monoolefin copolymer and at least one styrene diolefin copolymer. These blends have excellent platability and superior physical properties including enhanced rigidity, toughness, and dimensional stability.
(4: Metallizing Polymeric Substrates)
Nowadays plastic materials are frequently used for decorative parts in automotive and other applications due to their low cost and ease of processing/shaping by various means. It is well known in the art that plastic materials can be electroplated to achieve a particular aesthetic finish. Decorative chromium plating comprising successive electrodeposited layers of copper, nickel and chromium is the process of choice. The electrodeposit must adhere well to the underlying plastic substrate even in corrosive environments and when subjected to thermal cycling, such as are encountered in outdoor service. The prior art describes numerous processes for metallizing plastics to render them suitable for electroplating by conditioning the substrate's surface to insure electrodeposits adequately bond thereto resulting in durable and adherent metal deposits.
Liu in U.S. Pat. No. 4,604,168 (1986) describes a method of preparing the surface of molded mineral-filled Nylon® to receive an adherent electrodeposited metal coating comprising the steps of: exposing the surface to a plasma glow discharge; vacuum depositing a film of chromium or titanium onto the plasma-treated surface; vacuum depositing a nickel film onto the chromium or titanium film to prevent oxidation thereof; and then vacuum depositing a copper film onto the nickel film.
Stevenson in U.S. Pat. No. 4,552,626 (1985) describes a process for metal plating filled thermoplastic resins such as Nylon-6®. The filled resin surface to be plated is cleaned and rendered hydrophillic and preferably deglazed by a suitable solvent or acid. At least a portion of the filler in the surface is removed, preferably by a suitable acid. Thereafter an electroless plating is applied to provide an electrically conductive metal deposit followed by applying at least one metallic layer by electroplating to provide a desired wear resistant and/or decorative metallic surface.
Conrod in U.S. Pat. No. 5,376,248 (1994) describes a direct metallization process wherein plastic substrates may be electrolytically plated without the need for any prior electroless plating. The process uses a specially formulated post-activator composition at an elevated temperature to treat the activated substrate with an alkaline solution containing an effective amount of metal ions such as Cu+2 which undergo a disproportionation reaction.
Joshi in U.S. Pat. No. 6,645,557 (2003) describes a method for forming a conductive metal layer on a non-conductive surface by contacting the non-conductive surface with an aqueous solution or mixture containing a stannous salt to form a sensitized surface; contacting the sensitized surface with an aqueous solution or mixture containing a silver salt having a pH in the range from about 5 to about 10 to form a catalyzed surface; and electroless plating the catalyzed surface by applying an electroless plating solution to the catalyzed surface.
(5: Metal Plated Articles)
[Sports Articles]
Articles comprising metal-coated substrates made of plastics and composites are known in the prior art. Numerous articles, e.g., sporting goods, automotive parts, industrial components that are lightweight are prone to failure by breakage. For instance, fishing rod tip failure/breakage is a major cause of warranty returns of fishing rods to the manufacturer. As golf clubs are swung in close proximity to the ground, it is not unusual for the club head to strike the ground with considerable force, applying a large force or torque to the narrowest portion of the shaft, i.e. to the tip of the shaft that is joined to the club head. This impact can cause failure of the composite shaft at this point, causing the tip of the shaft to break at or closely adjacent to the club head.
Sandman in U.S. Pat. No. 5,538,769 (1969) describes a graphite composite shaft with a reinforced tip, suitable for use in fishing rods or golf clubs. The shaft includes a base shaft made at least partially of graphite composite material provided in one or more layers or plies. These shafts have relatively slender tips that are normally prone to impact damage. The reinforcement layer extends only part of the way up the length of the base shaft and is intended to render the shaft more resistant to impacts occurring at the tip thereby increasing the durability of the shaft without decreasing the performance of the fishing rod or golf club that incorporates the shaft. The reinforcement layer is applied by winding a suitable reinforcement tape around the outer periphery of the shaft.
Galloway in U.S. Pat. No. 6,692,377 (2004) describes an improved golf club shaft made of a composite material, such as carbon/epoxy, and a metal foil wrapped in a spiral pattern around at least a portion of the shaft body. The metal foil increases the torsional stiffness of the shaft and improves its bending stiffness, thereby enabling the first and second frequencies of the golf club to remain in a desired range.
Palumbo in U.S. Ser. No. 11/013,456 (2004), assigned to the applicant of this application, describes articles for automotive, aerospace, manufacturing and defense industry applications including shafts or tubes used, for example, as golf club shafts, ski and hiking poles, fishing rods or bicycle frames, skate blades and snowboards that are at least partially electroplated with fine-grained layers of selected metallic materials. Coated parts with complex geometry are described as well. Alternatively, articles such as conical or cylindrical golf club shafts, hiking pole shafts or fishing pole sections, plates or foils and the like can also be electroformed fine-grained metallic materials on a suitable mandrel or temporary substrate yielding strong, ductile, lightweight components exhibiting a high coefficient of restitution and a high stiffness.
Yanagioka in U.S. Pat. No. 4,188,032 (1980) discloses a nickel-plated golf club shaft made of fiber-reinforced material having on substantially its entire outer surface a metallic plating selected from the group consisting of nickel and nickel based alloys for the purpose of providing a wear-resistant coating. The electroless nickel coating of choice is 20 μm thick and the deposition time is 20 hrs, resulting in a deposition rate of 1 μm/hr.
Chappel in U.S. Pat. No. 6,346,052 (2002) discloses golf club irons with multilayer construction. The golf club head comprises a soft nickel alloy core and a hard chrome coating. The process used to produce the golf club heads involves an investment casting process in which the soft nickel alloy core is cast and the hard chrome coating is electroplated onto the core. Unlike the decorative chrome used on prior art golf clubs (hardness of about 35 to 45 Rockwell C, typical thickness between 0.05 to 0.2 mil) the chrome outer layer used in the invention is between 0.8 mils to about 1 mil (20 μm to 25 μm) thick, which is at least four times thicker than conventional applications of decorative chrome in prior art clubs. The hard chrome plating employed provides durability without compromising the superior feel characteristics of the relatively soft nickel alloy core when a golf ball is struck.
Heinrich in U.S. Pat. No. 6,679,788 (2004) discloses a golf club head where at least part of the striking face is coated with alloys of transition metals and metalloids with a hardness over 1,250 VHN by a thermal spraying method with average spray-particle velocities of over 500 m/s.
Although golf club heads and faceplates are primarily made of metal, polymeric materials can be used. In this context reference is made to Pond, U.S. Pat. No. 5,524,331 (1996) that discloses a method for casting a graphite-epoxy resin composite insert within a recess of a face of a metal golf club head. The objective of this approach is directed at displacing the weight away from the center and increasing the moment of inertia.
Schmidt in U.S. Pat. No. 5,485,997 (1996), discloses a golf putter head with a face plate insert composed of a non-metallic material such as an elastomer to enlarge the sweet spot and improve the peripheral weighting.
Numerous publications describe sport racquets reinforced and stiffened by structural straps or plates at the outer or inner surfaces, or within the wall of the handle and frame, including Stauffer (U.S. Pat. No. 3,949,988 (1976), Matsuoka in JP2000061005 (1998) and JP09285569 (1996).
Reed in U.S. Pat. No. 5,655,981 (1997) describes a shaft for a hockey stick comprising a non-metallic material coated first by a layer of a resilient yet tough polymeric material, a second layer comprised of a metal including aluminum, copper, gold and silver and a third layer comprised of a clear, resilient, tough material. The thin metallic layer is applied to the substrate by a vapor vacuum deposition process. The base layer, metallic layer and top layer have an overall thickness of less than 3 mils. The sole purpose of the thin metallic layer [maximum thickness of 0.01 mils (0.25 μm)], is to enhance the appearance.
[Polymer Ammunition Casings]
Burgess in U.S. Pat. No. 3,749,021 (1973) discloses a metal-plated plastic ammunition cartridge casing. A nickel or chromium metal film, preferably between 0.05 to 0.1 mils thick is plated onto a plastic cartridge case to increase the strength, abrasion and burn-through resistance as well as lubricity of the cartridge casing. The plastic casing may comprise a filled or a fiber reinforced plastic. A plated metal skin preferably 5 to 7 mils thick may also be employed in conjunction with non-reinforced plastic casings to increase the strength of the casing in selected areas.
Husseini in U.S. Pat. No. 6,845,716 (2005) discloses a molded plastic cartridge casing which is molded around at least a portion of the projectile. ZYTEL® resin, a modified 612 Nylon® resin to increase elastic response, available from E. I. DuPont De Nemours Co., and is a particularly suitable material for the cartridge casing. The base may be a metal base, such as a brass base, a plastic material base, a ceramic base, a composite base, or combinations thereof.
[Automotive Articles]
Various automotive articles made of plastics and composites optionally metal coated for appearance and corrosion protection are known in the prior art. Exterior automotive parts, such as a front end grilles or a wheel covers, generally contain thicker metal layers and are formulated to withstand a more aggressive environment than interior automotive parts or decorative parts for household appliances.
Wang in U.S. Pat. No. 6,010,196 (2000) describes a simulated chrome plated vehicle wheel formed by placing a thin, chrome plated wheel cover that is preferably constructed of a plastic substrate over a conventional, non-plated vehicle wheel. The wheel cover has a contour and includes surface patterns that are identical to the contour and surface patterns of the vehicle wheel thereby providing the appearance of a solid chrome plated vehicle wheel.
Vander Togtin U.S. Pat. No. 4,999,227 (1991) discloses an automotive bumper comprising a shell of injection molded platable grade ABS plastic. The plastic shell is plated with chromium metal and then backfilled by injection of ethylene ionomers. The composite structure has a pleasing metallic appearance, is lightweight, easy to manufacture yet has the structural integrity necessary to serve as impact resistant members on automobiles.
Luch in U.S. Pat. No. 4,429,020 (1984) describes metal-polymer composite articles, e.g., knobs, nuts, trimmings or ornaments, automotive components including grilles, headlamp bezels and surrounds, wheel covers, trim, hubs and like parts, having silvery hued metal surfaces. Suitable directly electroplateable polymeric materials include polyvinyls, polyolefins, polystyrenes, elastomers, polyamides and polyesters and contain carbon black and sulfur. The surface of the polymer is plated with an alloy of tin and Group VIII metals. A durable adherent Ni layer is disposed between the plastic body and the surface plating.
Anderson in U.S. Pat. No. 4,671,552 (1987) describes an improved grille guard made of rigid plastic plates such as ABS and Al or steel tubes for use on light truck-type vehicles, such as pickup trucks, vans and four-wheel drive vehicles which is substantially lighter (perhaps one-third the weight) and substantially cheaper (perhaps one-third the cost) of a comparable steel unit, yet may be provided with an appearance equivalent to a corresponding plated steel grille guard. The grille guards include end plates which may be reinforced.
Buckley in U.S. Pat. No. 6,802,232 (2004) describes brake and accelerator pedals for golf and utility vehicles made of molded plastic. The pedal arm assembly is injection molded such that the arm and the pedal member are integrally molded. The pedal arm assembly may include an internal reinforcement member that is encapsulated within the pedal arm assembly for improved structural rigidity.
Smith in U.S. application Ser. No. 10/700,887 (2003) discloses a running board for a passenger car or light truck consisting of an upper molded thermoplastic section having a Class A automotive finish and a lower section having reinforcing ribs and mounting brackets. The upper section includes three layers: a paint film having a Class A automotive finish, a thin layer of thermoplastic polyolefin (TPO) and a thick layer of polypropylene. The lower section is homogeneous and may be a plastic such as TPO, polypropylene or high-density polyethylene (HDPE), which may further contain chopped, randomly oriented glass reinforcing fibers. The two sections are secured to one another about their peripheries by autogenous bonding.